Method for igniting several fluorescent lamps and circuit arrangement for carrying out this method



March 5, 1968 H. ELFERS 3,

METHOD FOR IGNITING SEVERAL FLUORESCENT LAMPS AND CIRCUIT ARRANGEMENT FOR CARRYING OUT THIS METHOD Filed NOV. 5, 1963 Invenlar: HENRY EL FERSV $5 'W AG E N T United States Patent 3,372,301 METHOD FOR IGNlTlNG SEVERAL FLUORES- CENT LAMPS AND CIRCUIT ARRANGEMENT FGR CARRYING OUT THIS METHOD Henry Elfers, Hamburg, Germany, assignor to Lumoprint Zindler K.G., Hamburg, Germany, a corporation of Germany Filed Nov. 5, 1963, Ser. No. 321,613 Claims priority, application Germany, Nov. 15, 1962,

L 43,456 Claims. (Cl. 315-106) The invention relates to a method for igniting several fluorescent lamps equipped with preheatable spiral-type or coil filaments which are preheated in order to produce the simultaneous ignition of the several lamps. The invention also comprises a circuit arrangement for carrying out this method.

1" he present invention aims particularly at applications, in which the simultaneous illumination of a group of such fluorescent lamps is an important factor. Such applications are, for example, the lighting equipment of photostat copying apparatus or of photographic reproduction apparatus or the like. If, in apparatus of this kind, the simultaneous commencement of illumination or starting of the lamps is not ensured, the image transfer results may be adversely affected, because the exposure is affected by unpredictable and nonuniform light intensity, and more particularly lesser intensities of short duration. These applications form, therefore, a particularly preferred embodiment of the invention.

It is already known to excite groups of several fluorescent lamps for simultaneous ignition upon the application of the mains (line) voltage, by preheating these lamps with a reduced voltage of, say, about 5 volts. Such preheating which is adapted to the capacitance of the spiral or electrodes, is generally insuflicient because occa sionally, for example in some 2% of all cases, faulty ignition can occur.

The present invention aims at providing a method and a circuit arrangement whereby these drawbacks may be avoided.

It is a further object of the invention to provide a circuit arrangement or equipment, whereby the complicated hitherto use-d arrangements for raising the operating voltage at the instant of ignition are eliminated.

It is yet another object of the invention to provide a simple circuit arrangement, adapted to the ignition of a pluraliy of fluorescent lamps equipped with preheatable spirals in which this simplification is combined with reliability of operation.

According to the invention, the heating voltage is briefly raised during or before the switching on of the fluorescent lamps. This short-duration super-elevation of the voltage lasts preferably only 0.2 second. During this application of the higher voltage a temperature is developed which, in view of the thermal capacity of the spiral, is suflicient to ensure a suflicient spiral temperature and thereby the absolutely reliable ignition even in the least favourable case, in which the ignition is switched on during the zero" point in the sine wave of the mains voltage. In this case, the actual ignition takes place when the mains voltage rises again.

According to the circuit arrangement for carrying out the method of the invention, an operating switch for several fluorescent lamps is associated with a change-over switch which applies in one position the preheating voltage, and in the other position, corresponding to the lamp ignition, switches from the preheating voltage to the operating voltage so that the operating voltage acts for a short period as the elevated heating voltage.

According to a preferred embodiment of the invention,

3,3723% Patented Mar. 5, 1968 there is provided a relay, referred to hereinafter as a preheating relay, having working contacts connected to the lamps and adapted to apply the heating voltage to the spiral whilst bridging the lamps; this relay is tie-energized as a function of an actuating movement of the operating switch, whilst the change-over switch is switched before the opening of said working contacts in order to raise the voltage applicable to the lamp leads.

According to another preferred embodiment of the invention, a relay is connected in series with the operating switch, having a rest contact in the circuit of the preheating relay, and the change-over switch in the preheating circuit, wherein the rest contact controls the application of a reduced voltage and the working contact the application of a raised voltage to the lamps. Whilst in some applications the switching constant of the preheating relay, possibly in conjunction with the relay connected in series with the operating switch, is suflicient to produce the required time lag for opening the working contacts of the preheating relay connected in parallel to the lamps, according to a special embodiment of the invention the preheating relay is a relay responding with a time lag.

According to a further embodiment of the invention, the breaker contact is located in the circuit of the preheating relay and the change-over contact for changing the voltage applied to the lamps is located on the operating switch so that a second relay becomes unnecessary. Here, the arrangement of the operaitng switch may be such that its actuation causes directly the switching of the changeover contact whilst the preheating relay is also tie-energized immediately, if it is a time lag relay or if its time constant is comparatively large, or it may be tie-energized with a certain time lag if its time constant is small. The essential feature is that the reversing switch becomes operative as a function of the actuation of the operating switch before the opening of the bridging contacts mounted in parallel to the lamps, causing the operating voltage to act as raised ignition voltage during the initial stages.

According to a further preferred embodiment of the invention, an autotransformer is connectable by a mains switch to the voltage supply; this autotransformer has a tap so that its full voltage serves as raised heating voltage and as operating voltage whilst its tap supplies a reduced preheating voltage, controlled by the change-over switch according to the actuation of the operating switch, the arrangement being such that the circuit for the operating switch is located between the main switch and the fluorescent lamps.

According to an essential feature of the invention, several fluorescent lamps or groups of fluorescent lamps have only a single, common current lead for the preheating, the short-duration raised heating, and the supply of the ignition and operating current and the corresponding voltage, respectively, wherein there is provided on the input side of the circuit a change-over switch between two voltage values, the lower supplying the preheating voltage and the higher the raised preheating voltage and the ignition and operating voltage. The difference between the raised preheating voltage on the one hand, and the ignition and operating voltage on the other hand, is controlled by operating contacts shunted to the individual lamps.

In another preferred embodiment said operating switch may be, for example, a mechanical timing device which re-opens after the closure of the switch after a certain and adjustable period of time.

It is here essential that the remaining circuit members should be connected in series to the main switch. This has the advantage that a low preheating is continuously available so as to guarantee the immediate ignition on the actuation of the operating switch after the application of the raised heating voltage. It is also essential that the U contacts connected in parallel should switch oil? the heating voltage during the time in which the lamps are ignited so as to prevent undesirable overloading of the heating spirals. With the circuit according to the invention, this is realized with a minimum of circuitry between the lamp units and the circuit elements.

Further advantages and features of the invention will become apparent from the following description, with reference to the accompanying drawing showing, by way of example, embodiments of the invention, and in which:

FIG. 1 shows a first embodiment of a circuit according to the invention; and

FIG. 2 shows a second embodiment of the circuit according to the invention.

In the drawings, identical parts are marked with the same reference numerals.

The circuit comprises an electric voltage source 1 with two terminals and two groups of lamps, each consisting in this case of two fluorescent lamps 2, 3, and 4, 5, respectively, which are connected in series. This series circuit is governed by the type of the lamp and by the voltage values.

Connected to the terminals of the voltage source is the winding 6 of an autotransformer, having a center tap 7. The ends of the winding 6 are connected, on the one hand through leads 8, and 9, 10, respectively, with one side 23, 24 of the groups of fluorescent lamps, and on the other hand through a lead 11 to a change-over switch 12. This change-over switch 12 has a working contact 13, connected to the lead 11, and a rest contact 14, connected through a lead 15 to the tap 7. A contact arm 16 of the change-over switch is connected to the other sides 21, 22 of the lamp circuits through leads 17 and 18, containing cut-in apparatus 19, 20.

A main switch 26 is located in the connecting lead between the voltage source 1 and the autotransformer 6. A cut-in 27 is connected, for example, through the lead 9, to the side of the main switch 26 remote from the voltage source, containing an operating switch 28 in the form of a mechanical timing device, that is to say, a timing switch, the time constant of which may be adjustable additionally by electric delaying means, such as a bi-metallic strip.

In FIG. 1, the operating switch 28 is mounted in series with a relay 29. This series circuit is connected by a lead 44 with the other terminal of the voltage source 1.

Parallel to the series circuit of operating switch 28 and relay 29, a further relay 30 is connected through a rectifier 31 and a rest contact 32 of the relay 29. In the embodiment shown, this relay 30, or preheating relay, is a time-lag release relay, comprising preferably a shunted capacitor 33 which is charged during the energization of the relay 30 and discharged on the interruption of the energizing circuit for this relay Whilst initially maintaining an excitation voltage which causes the time lag. The change-over switch 12 is in this embodiment a changeover contact of the relay 29, wherein the contact 14 acts as rest contact and the contact 13 as working contact.

The lamps 2, 3, and 4, 5 respectively, always forming a group, are connected in series by leads 34, 35. In addition, the groups of lamps, 2, 3 and 4, 5 respectively are each provided through a lead 36, 37, 38, 39 with a switch 40, 41, 42, 43, connected in parallel to the lamps. In the embodiment shown, these switches 40 to 43 are working contacts of the preheating relay.

Actuation of the main switch 26 causes the preheating relay 30 to be energized through the leads 9, 27, the rest contact 32 and the lead 44. The working contacts 40, 41, 42, 43 are closed and a reduced heating voltage is applied to the groups of lamps; this heating voltage is taken from the winding 6 of the autotransforrner between the terminal for the leads 8, 9 and the tap 7, and is applied through the change-over switch 12 to the lamps. In this manner, the ignition is prepared by a preheating, lasting for, say, five seconds, at a voltage of 5 volts.

When the operating switch 28 is closed, the relay 29 is energized. Its rest contact 32 opens and tie-energizes the preheating relay 30. Simultaneously, the switch arm 16 of the change-over switch 12 moves into contact with the working contact 13 so that the full operating voltage of the winding 6 of the autotransformer is applied to the groups of lamps through the leads 17, 18. Since the preheating relay 30 responds with a time lag or in accordance with its time constant, its working contacts 40 to 43 remain initially closed so that the spiral or electrodes are affected by a higher voltage as heating voltages. The contacts 40 to 43 are preferably released after /5 of a second; this may be included into the control by means of an operating switch, associated with, or formed by a time clock 48. Since now the full voltage of the winding 6 is being applied to the sides 21, 23, and 22, 24, respectively, of the groups of lamps, the immediate ignition after the release of the preheating relay 30 is reliably effected.

When a time clock is used as operating switch 28, this switch may be opened again, for example, after the lighting up time. This de-energizes the relay 29, its rest contact closes, so that with closed main switch 26 the energizing circuit of the preheating relay 30 is closed when the main switch 26 is closed. In addition, the switch arm 16 of the change-over switch 12 of the relay 29 makes contact with the rest contact 14 so that the groups of lamps receive a reduced voltage, that is, the normal preheating voltage during the time, during which the main switch 26 is closed.

The arrangement may therefore be immediately switched on since the ignition occurs automatically after an automatic preheating time of about 0.2 second, wherein the contacts 40 to 43, connected in parallel to the lamps and closed during the energization of the preheating relay 30, are automatically opened after the de-energization of the relay and in accordance with the time lag or time constant.

Obviously, the arrangement may be modified in various ways without thereby departing from its principle. For example, as shown in FIGURE 2, the relay 29 may be omitted and the change-over switch 12 and the switch 32 may be actuated in a mechanical coupling 45, 46 by means of the actuating member of the operating switch 28. Here, there is also the possibility of providing a delay for the contact 32 or directly for the switch 49 to 43 by means of the local switching conditions or by connected delaying members 47.

The invention comprises more particularly a circuit arrangement for a lighting installation to be actuated repeatedly always for short periods of time, comprising several low-voltage fluorescent lamps which must ignite simultaneously, the electrodes of these lamps being preheated during the dark intervals with a low preheating voltage, corresponding to a minimum temperature, wherein the operating voltage is applied to the lamps for their ignition and for the lighting up only when the electrodes have been sufliciently preheated. The essential features of a circuit arrangement of the kind hereinbefore described are that the electrode bridge branches of the lamps have starter contacts which are opened together with a time lag when the lighting switch applying the f ull operating voltage to the lamps is opened; that the lighting switch is associated with a change-over switch, connecting in its rest position the electrodes of the lamps with the minimum preheating voltage source and switching on actuation of the lighting switch automatically the connection from the lamp electrodes to the operating voltage before the starter contacts in the electrode bridge branches open, so that the operating voltage applied to the lamps becomes effective shortly before the ignition to supply an elevated electrode heating voltage. The term starter contact signifies here the working contacts 40 to 43, and the operating switch 28 serves as lighting switch. The circuits 36 to 39, in which the starter contacts 40 to 43 are located, form the electrode bridge branches.

In addition, the preheating relay may here be regarded as the starter relay.

The invention is not limited to the embodiment shown, and the many modifications are possible within the art and without departing from the principle of the invention which is defined and circumscribed by the accompanying claims.

Having thus fully disclosed my invention, what I claim and desire to secure by Letters Patent is:

1. A method of operating a plurality of fluorescent lamps each having respective heaters and energizable with passage of current therethrough and adapted to sustain a discharge through the lamps effecting illumination thereof, comprising the steps of:

(a) applying a relatively low voltage to said heaters for passing a corresponding current therethrough to preheat s-aid lamps at a level less than sufiicient to produce illumination thereof;

(b) connecting a relatively high voltage across said lamps While delaying the illumination thereof by temporarily preventing discharge in said lamps;

(c) energizing said heaters with said high voltage simultaneously with the connection of said relatively high voltage across said. lamps in step (b) for a short predetermined period to pass an elevated current through said heaters suificient to raise the heater temperatures to a level inducing the simultaneous discharge in said lamps at said higher voltage; and

(d) terminating the passage of current through said heaters while maintaining high voltage across said lamps upon termination of said predetermined short period to illuminate said lamps simultaneously.

2. A circuit arrangement for operating a plurality of fluorescent lamps each having a pair of heaters energizable for the passage of an electric current through said heaters preparatorily to the illumination of said lamps and sustaining a discharge through said lamps for illumination thereof, said circuit arrangement comprising:

transformer means having a high-voltage output and a low-voltage output and being energizable by a source of alternating current;

a main switch in circuit with said transformer means and said source and actuatable for electrically energizing said transformer means from said source;

a two-position switch in circuit with said heaters and having a first position wherein said low-voltage output of said transformer means is connected across said heaters and a second position wherein said highvoltage output of said transformer means is connected across said heaters; and

a control network energized by transformer means for initiating said discharge through said lamps, said network including an operating switch for controling said two-position switch and operating same upon actuation of said main switch and after the lapse of a period of energization of said heaters in said first position of said two-position switch to shift same to said second position and apply high voltage to said heaters prior to the initiation of said discharge.

3. A circuit arrangement as defined in claim 2, further comprising a bridge network connecting each of the heaters of said lamps in series and including a respective switch, said control network including a time-delay relay for operating said switches of said bridge networks to initiate said discharges through said lamps.

4. A circuit arrangement as defined in claim 3 wherein said two-position switch is operatively connected to said time-delay relay.

5. A circuit arrangement as defined in claim 3, further comprising a mechanical linkage having delay means connected between the armature of said time-delay relay and said two-position switch.

6. A circuit arrangement as defined in claim 3 wherein said control network includes a control relay in series with said operating switch and actuating said two-position switch.

7. A circuit arrangement as defined in claim 2 wherein said fluorescent lamps are arranged in at least two lamp circuits with the respective lamps thereof connected in series, each of said lamp circuits being connectable in parallel across the transformer means by said two-position switch.

8. A circuit arrangement for operating a plurality of fluorescent lamps connected in a common circuit and each having a pair of heaters energizable for the passage of an electric current through said heaters preparatorily to the illumination of said lamps and sustaining a discharge through said lamps for illumination thereof, said circuit arrangement comprising:

a high-voltage source capable of effecting discharge through said lamps upon the heating thereof and a low-voltage source of a level insufficient to ignite said lamps;

a two-position switch in circuit with said heaters and having a first position wherein said low-voltage source is connected across said heaters and a second position wherein said high-voltage source is connected across said heaters; and

a control network energized by said high-voltage source for initiating said discharge through said lamps, said network including an operating switch, and means operatively connecting said operating switch and said two-position switch for operating same after the lapse of a period of energization of said heaters in said first position of said two-position switch to shift same to said second position and apply high voltage to said heaters prior to the initiation of said discharge.

9. A circuit arrangement as defined in claim -8, further comprising a bridge network connecting the heaters of each of said lamps in series and including a pair of starter contacts openable to disconnect the heaters of each lamp from one another; and a time-delay relay in said control network having a contact operable to open-circuit said time-delay relay and operatively connected to said starter contacts for opening same to initiate said discharge.

10. A circuit arrangement as defined in claim 9 wherein said control network includes a further relay connected in series with and energizable by said operating switch and controlling said two-position switch, said contact of said time-delay relay being operable by said further relay.

References Cited UNITED STATES PATENTS 2,290,819 7/1942 Warshawsky 315-107 2,697,801 12/1954 Hamilton 315-107 2,813,227 11/1957 Sweet 3l5107 JOHN W. HUCKERT, Primary Examiner.

J. R. SHEWMAKER, Assistant Examiner. 

8. A CIRCUIT ARRANGEMENT FOR OPERATING A PLURALITY OF FLUORESCENT LAMPS CONNECTED IN A COMMON CIRCUIT AND EACH HAVING A PAIR OF HEATERS ENERGIZABLE FOR THE PASSAGE OF AN ELECTRIC CURRENT THROUGH SAID HEATERS PREPARATORILY TO THE ILLUMINATION OF SAID LAMPS AND SUSTAINING A DISCHARGE THROUGH SAID LAMPS FOR ILLUMINATION THEREOF, SAID CIRCUIT ARRANGEMENT COMPRISING: A HIGH-VOLTAGE SOURCE CAPABLE OF EFFECTING DISCHARGE THROUGH SAID LAMPS UPON THE HEATING THEREOF AND A LOW-VOLTAGE SOURCE OF A LEVEL INSUFFICIENT TO IGNITE SAID LAMPS; A TWO-POSITION SWITCH IN CIRCUIT WITH SAID HEATERS AND HAVING A FIRST POSITION WHEREIN SAID LOW-VOLTAGE SOURCE IS CONNECTED ACROSS SAID HEATERS AND A SECOND POSITION WHEREIN SAID HIGH-VOLTAGE SOURCE IS CONNECTED ACROSS SAID HEATERS; AND A CONTROL NETWORK ENERGIZED BY SAID HIGH-VOLTAGE SOURCE FOR INITIATING SAID DISCHARGE THROUGH SAID LAMPS, SAID NETWORK INCLUDING AN OPERATING SWITCH, AND MEANS OPERATIVELY CONNECTING SAID OPERATING SWITCH AND SAID TWO-POSITION SWITCH FOR OPERATING SAME AFTER THE LAPSE OF A PERIOD OF ENERGIZATION OF SAID HEATERS IN SAID FIRST POSITION OF SAID TWO-POSITION SWITCH TO SHIFT SAME TO SAID SECOND POSITION AND APPLY HIGH VOLTAGE TO SAID HEATERS PRIOR TO THE INITATION OF SAID DISCHARGE. 